1. Field of the Invention
This invention relates, in general, to a current amplifier and more specifically to a current amplifier having a single control amplifier wherein logic selects one of a plurality of output stages.
2. Background Art
Current amplifiers typically have a control amplifier with a first current supplied by a current source and a second current that is multiplied due to the resistance values in the control amplifier.
In order to produce different output currents, one known configuration provides separate control amplifiers and output stages for each output current desired. However, this configuration requires a relatively large amount of area when placed on an integrated circuit chip and therefore increases the cost proportionally. Furthermore, the outputs cannot be varied once the mask of the chip is manufactured and an output compensation capacitor is required for each output stage.
Another known configuration changes a reference current to provide different outputs. However, this requires additional circuitry to change the reference current and does so with PNP transistors which slows the response time drastically.
Thus, what is needed is a current amplifier wherein one output current is digitally selected from more than one current, the ratio of outputs available may be varied during metalization of the chip, and the outputs may be compensated by a single capacitor.